-SUBJECT- SYNTH,SEMI SYNTH OR MINERAL.

[lombardi]

This subject has been discussed at length in this forum,so much so that i am confused-i am about to undertake my first oil change since purchase of my 86 gtv6 grand prix and i am at odds on wether to use min or synth oil,engine was re-built 2 years ago and looks brand new,have read arguments on why i should use 20-50 mineral and why i should use synth,the mech that did to the rebuilt says i should use mineral,what do u think.ciao and regards

[dehne]

hi there ive been using castrol magnatec in my v6 for the last 6years and its been great so ill recomend it highly

[lombardi]

Very interesting,i believe this is a semi synth oil,u are the only one that has recom this oil and i believe u are on the money.rgrds

[bonkfrog]

Hi Lombardi

I've become increasingly disenchanted by oil companies use of the term synthetic. Even Mobil 1 isn't a real synthetic but, apparently, they are legally OK to call it synthetic, even though it's simply a modified and very refined mineral oil. There are real synthetics but the cost is high. I understand that Redline make several synthetics, including their 75W-90RS for Alfetta transmissions - about $165 for 3.8 litres! Word is it's good though. Any others using it?

[Doug Gould]

I believe that Mobil 1 is synthetic, although Mobil also has semi-synthetics. The oil companies use synthetic oil blended with mineral oil as a viscosity modifier. These oils are generally called semi-synthetic. Personally, I'm not keen on halfway houses. The thing with oils is that you never know if its been good until you tear down the engine. The additive pack that is used is possibly more important, but gets little attention. Mobil have nearly half the Australian oil market because many oils are Mobil base oil branded by whoever adds the additive pack. Guys like Penrite don't have refineries. In Australia refineries are the domain of Shell, Mobil, BP & Caltex. So, unless the oil is imported its coming from one of those. The additive pack standard is designated by the API code: SL, SM, etc. I forget the latest level. Some oils can be up to 2 levels behind. Pennzoil were renowned for their additive pack, but they are now owned by Shell and I'm not sure if they still use the US imported additive pack. Most Australian oils use standard packs from Lubrizol.

As a rule, the more you change oil, the less critical it is. Synthetic is primarily better because the molecule chains don't break down (we need a chemist like Stuart Thomson). So, if you change oil frequently its less critical. Synthetics have traditionally been not so good with big engines with lots of sliding friction, eg pushrod V8's & aircraft engines (where its banned). However, it may be that this has been improved.

The oil I buy is chosen on a mix of what's cheap, brands I like, vehicle  is intended for (the Montreal gets good old fashioned mineral 20W50, the GTV6 gets Castrol Synthetic) and mood.

I used to use thick oil for the GTV6 because it tends to burn a bit and its main use is sprints. Then I changed to (I think) 10W60 Castrol synthetic because it was on special. I started using Castrol 5W30 because I had a fair bit left over from a job and it stopped burning oil. Go figure!

Doug

[franck]

i use mobile super XHP seems very good, pressure indication cold and hot seems correct, consumtion maybe 500mls to 5k although i change it and filter every 5k, run golden lodge plugs and on inspection indication also seems good.

[lombardi]

Thanks for all youre valuable reply's,SHELL have a new range in particular the 20-50 mineral with they claim new cleaning technology,think ill go for this one.rgrds ciao

[lombardi]

Have settled for NULON 15-40 mineral,everyone has opinions on oils,the consensus is that the most important bfactor is changing oil and filter frequently-ie every 5k.ciao

[carjunky]

I have redline transmission oil in the gearbox, it is fantastic, shifts beautifully from start up.
I use Mobil 1 5/50 and am very happy with it. It is much kinder to the engine when cold, that is when most wear takes place.

[GTV6SA]

a good indiction of a 'good oil' is to inspect the cam buckets and lobes, if they show signs of wear , you are using the 'wrong type of oil' BP corse plus was better than any Shell/mobil 1 but now is maketed under the Castrol edge sport 20w50 mineral best of 'synthetics is NEO, expensive but engine pulled down after 10 years of racing , componets are still "brand new"

[lombardi]

Whats NEO-never heard of it-what brand?